Last spring frost
Mar 7
Frost Dates for Tonto Basin, AZ
First fall frost
Nov 20
Growing season
255 days
Hardiness zone
9a
In an average year around Tonto Basin, AZ, the last spring frost (32°F) is about Mar 7 and the first fall frost is about Nov 20, giving roughly a 255-day growing season. To be safe most years, wait until Feb 13 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Apr 16 | Mar 27 | Mar 11 |
| Freeze (32°F) | Mar 27 | Mar 7 | Feb 13 |
| Hard (28°F) | Mar 7 | Feb 15 | Jan 20 |
| Severe (24°F) | Feb 21 | Jan 26 | Dec 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 16 | Apr 8 | Apr 3 | Mar 31 | Mar 27 | Mar 23 | Mar 20 | Mar 16 | Mar 11 |
| 32°F | Mar 27 | Mar 19 | Mar 14 | Mar 10 | Mar 7 | Mar 4 | Mar 1 | Feb 24 | Feb 13 |
| 28°F | Mar 7 | Mar 2 | Feb 26 | Feb 20 | Feb 15 | Feb 9 | Feb 3 | Jan 31 | Jan 20 |
| 24°F | Feb 21 | Feb 12 | Feb 5 | Jan 31 | Jan 26 | Jan 19 | Jan 12 | Jan 6 | Dec 28 |
| 20°F | Feb 6 | Jan 30 | Jan 20 | Jan 13 | Jan 9 | Jan 3 | Dec 30 | Dec 24 | Dec 18 |
| 16°F | Jan 31 | Jan 29 | Jan 20 | Jan 16 | Jan 8 | Jan 5 | Jan 3 | Jan 2 | Dec 26 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Oct 25 | Nov 10 | Nov 22 |
| Freeze (32°F) | Nov 3 | Nov 20 | Dec 3 |
| Hard (28°F) | Nov 16 | Dec 1 | Dec 17 |
| Severe (24°F) | Nov 27 | Dec 15 | Jan 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 25 | Oct 31 | Nov 4 | Nov 6 | Nov 10 | Nov 13 | Nov 15 | Nov 18 | Nov 22 |
| 32°F | Nov 3 | Nov 10 | Nov 14 | Nov 17 | Nov 20 | Nov 22 | Nov 25 | Nov 29 | Dec 3 |
| 28°F | Nov 16 | Nov 21 | Nov 25 | Nov 27 | Dec 1 | Dec 4 | Dec 7 | Dec 11 | Dec 17 |
| 24°F | Nov 27 | Dec 2 | Dec 7 | Dec 11 | Dec 15 | Dec 19 | Dec 22 | Dec 27 | Jan 5 |
| 20°F | Dec 10 | Dec 15 | Dec 21 | Dec 25 | Dec 28 | Dec 31 | Jan 5 | Jan 13 | Jan 27 |
| 16°F | Dec 26 | Jan 1 | Jan 2 | Jan 4 | Jan 8 | Jan 14 | Jan 18 | Jan 28 | Jan 31 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Punkin Ctr, Az, about 6.4 miles away@if(!empty($station['elevation_ft'])), at 2,325 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Tonto Basin, AZ?
On average, the last spring frost (32°F) around Tonto Basin, AZ is about Mar 7. In cooler years it can run later, so for a safer bet many gardeners wait until Feb 13.
When is the first frost in the fall?
The first fall frost around Tonto Basin, AZ typically arrives about Nov 20. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Mar 7 on average, or Feb 13 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 255 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 85553 Planting calendar → Arizona frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026